function wigb (a,scal,x,z,amx)
%WIGB: Plot seismic data using wiggles
%
%  WIGB(a,scal,x,z,amx) 
%
%  IN    a: seismic data
%        scale: multiple data by scale
%        x: x-axis;
%        z: vertical axis (time or depth)
%         x and z are vectors with offset and time.
%
%         If only 'a' is enter, 'scal,x,z,amn,amx' are decided automatically; 
%         otherwise, 'scal' is a scalar; 'x, z' are vectors for annotation in 
%         offset and time, amx are the amplitude range.
%
% Author:
%         Xingong Li, Dec. 1995
% Changes: 
%        Jun11,1997: add amx
%         May16,1997: updated for v5 - add 'zeros line' to background color
%         May17,1996: if scal ==0, plot without scaling
%         Aug6, 1996: if max(tr)==0, plot a line 

if nargin == 0, nx=10;nz=10; a = rand(nz,nx)-0.5; end;
[nz,nx]=size(a); trmx= max(abs(a));
if (nargin <= 4); amx=mean(trmx);  end;
if (nargin <= 2); x=[1:nx]; z=[1:nz]; end;
if (nargin <= 1); scal =1; end;
if nx <= 1; disp(' ERR:PlotWig: nx has to be more than 1');return;end;

% take the average as dx
  dx1 = abs(x(2:nx)-x(1:nx-1)); dx = median(dx1); dz=z(2)-z(1);
  xmx=max(max(a)); xmn=min(min(a)); 

if scal == 0; scal=1; end;
a = a * dx /amx; a = a * scal;
fprintf(' PlotWig: data range [%f, %f], plotted max %f \n',xmn,xmx,amx);

% set display range 
x1=min(x)-2.0*dx; x2=max(x)+2.0*dx; z1=min(z)-dz; z2=max(z)+dz;

set(gca,'NextPlot','add','Box','on','XLim', [x1 x2],'YDir','reverse','YLim',[z1 z2]);
fillcolor = [0 0 0]; linecolor = [0 0 0]; linewidth = 1;
z=z';         % input as row vector
zstart=z(1); zend  =z(nz);

for i=1:nx,
   
  if trmx(i) ~= 0;    % skip the zero traces
        tr=a(:,i);         % --- one scale for all section
          s = sign(tr) ;
          i1= find( s(1:nz-1) ~= s(2:nz) );        % zero crossing points
        npos = length(i1);

        %12/7/97 
        zadd = i1 + tr(i1) ./ (tr(i1) - tr(i1+1)); %locations with 0 amplitudes
        aadd = zeros(size(zadd));

        [zpos,vpos] = find(tr >0);
        [zz,iz] = sort([zpos; zadd]);         % indices of zero point plus positives
        aa = [tr(zpos); aadd]; aa = aa(iz);

        % be careful at the ends
        if tr(1)>0,        a0=0; z0=1.00; else a0=0; z0=zadd(1); end;
        if tr(nz)>0, a1=0; z1=nz; else a1=0; z1=max(zadd); end;
                        
        zz = [z0; zz; z1; z0]; aa = [a0; aa; a1; a0];
        zzz = zstart + zz*dz -dz;
        patch( aa+x(i) , zzz,  fillcolor);
        line( 'Color',[1 1 1],'EraseMode','background',  ...
         'Xdata', x(i)+[0 0], 'Ydata',[zstart zend]); % remove zero line

%'LineWidth',linewidth, ...
%12/7/97 'Xdata', x(i)+[0 0], 'Ydata',[z0 z1]*dz);        % remove zero line

    line( 'Color',linecolor,'EraseMode','background','LineWidth',linewidth, ...
         'Xdata', tr+x(i), 'Ydata',z);        % negatives line

   else % zeros trace
        line( 'Color',linecolor,'EraseMode','background','LineWidth',linewidth, ...
         'Xdata', [x(i) x(i)], 'Ydata',[zstart zend]);
   end;
end;